The present invention relates to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions containing magnetite. More specifically, the present invention in embodiments relates to processes for the preparation of a toner composition by a chemical process, such as emulsion aggregation, wherein the latex particles are aggregated with the colorant particles such as magnetite comprised of iron oxides, and wherein such particles can simultaneously function as colorant particles and as a coagulating or flocculating agent and thereafter coalescing or fusing to provide toner size particles which when developed by an electrographic process generates documents suitable for magnetic image character recognition or MICR. Also, in embodiments the present invention relates to the use of magnetite particles, which exhibits a negative or an anionic charge of about xe2x88x922 to about xe2x88x9240 coulombs per square centimeter (coulombs/cm2) at high pH conditions such as, for example, from about 6.5 to about 10, and which magnetite can function as a coagulating or flocculating agent for cationically charged species, or components.
In U.S. Pat. No. 6,132,924, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant a latex and a coagulant, followed by aggregation and coalescence, wherein the coagulant may be a polyaluminum chloride.
In U.S. Pat. No. 6,268,102, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant a latex,and a coagulant, followed by aggregation and coalescence, wherein the coagulant may be a polyaluminum sulfosilicate.
Illustrated in U.S. Pat. No. 5,994,020, the disclosure of which is totally incorporated herein by reference, are toner preparation processes, and more specifically, a process for the preparation of toner comprising
(i) preparing, or providing a colorant dispersion;
(ii) preparing; or providing a functionalized wax dispersion comprised of a functionalized wax contained in a dispersant mixture comprised of a nonionic surfactant, an ionic surfactant, or mixtures thereof;
(iii) shearing the resulting mixture of the functionalized wax dispersion (ii) and the colorant dispersion (i) with a latex or emulsion blend comprised of resin contained in a mixture of an anionic surfactant and a nonionic surfactant;
(iv) heating the resulting sheared blend of (iii) below about the glass transition temperature (Tg) of the resin particles;
(v) optionally adding additional anionic surfactant to the resulting aggregated suspension of (iv) to prevent, or minimize additional particle growth of the resulting electrostatically bound toner size aggregates during coalescence (iv);
(vi) heating the resulting mixture of (v) above about the Tg of the resin; and optionally,
(vi) separating the toner particles.
With respect to the references only a small part thereof has been selected and this part may or may not be fully representative of the prior art teachings or disclosures.
Magnetic ink printing methods with inks containing magnetic particles are known. For example, there is disclosed in U.S. Pat. No. 3,998,160 that various magnetic inks have been used in printing digits, characters, or artistic designs, on checks or bank notes. The magnetic ink used for these processes contains, for example, acicular magnetic particles, such as magnetite in a fluid medium, and a magnetic coating of ferric oxide, chromium dioxide, or similar materials-dispersed in a vehicle comprising binders and plasticizers. According to the disclosure of the ""160 patent there is provided a method of printing on a surface with an ink including acicular magnetic particles permitting the authenticity of the printing can be verified, and wherein a pattern is formed on a carrier with the ink in the wet state, and wherein the particles are subjected to a magnetic aligning process while the ink is on the carrier.
Disclosed in U.S. Pat. No. 4,128,202 is a device for transporting a document that has been mutilated or erroneously encoded wherein there is provided a predetermined area for the receipt of correctly encoded magnetic image character recognition information (MICR). As indicated in this patent, the information involved is referred to as MICR characters, which characters appear, for example, at the bottom of personal checks as printed numbers and symbols. These checks have been printed in an ink containing magnetizable particles therein, and when the information contained on the document is to be read, the document is passed through a sorter/reader which first magnetizes the magnetizable particles, and subsequently detects a magnetic field of the symbols resulting from the magnetic retentivity of the ink. The characters and symbols involved, according to the ""202 patent, are generally segregated into three separate fields, the first field being termed a transient field, which contains the appropriate symbols and characters to identify the bank, bank branch, or the issuing source. The second field contains the account affected by the transactions, and the third field, which is not prerecorded, indicates the amount of the check.
In U.S. Pat. No. 5,914,209, the disclosure of which is totally incorporated by reference, there is illustrated a process of preparing MICR toners using a combination of hard and soft magnetites and lubricating wax in the formulation and melt mixing with a resin followed by jetting and classifying the blend to provide toner compositions.
In U.S. Pat. No. 4,517,268, the disclosure of which is totally incorporated by reference, there is illustrated a process for the preparation of MICR toners by melt mixing the appropriate components in a Banbury apparatus, following by pulverizing the magnetite and the resin, and then jetting and classifying to provide, for example, about 10 to about 12 micron toner size particles which when mixed with an additive package and carrier can provide a developer suitable for the Xerox Corporation 9700(copyright).
Other patents relating to MICR processes include U.S. Pat. Nos. 4,859,550; 5,510,221, and 5,034,298.
In U.S. Pat. No. 5,780,190, the disclosure of which is totally incorporated herein by reference, there is disclosed an ionographic process which comprises the generation of a latent image comprised of characters; developing the image with an encapsulated magnetic-toner comprised of a core comprised of a polymer and soft magnetite and wherein the core is encapsulated within a polymeric shell; and subsequently providing the developed image with magnetic ink characters thereon to a reader/sorter device.
Illustrated in U.S. Pat. No. 4,758,506, the disclosure of which is totally incorporated herein by reference, are single-component development cold pressure fixable toner compositions, wherein the shell selected can be prepared by an interfacial polymerization process. Also known are single component magnetic cold pressure fixable toner compositions comprised of magnetite and a polyisobutylene encapsulated in a polymeric shell material generated by an interfacial polymerization process.
In situations requiring MICR capabilities the toners selected usually contain magnetites having specific properties, an important one of which is a high enough level of remanence or retentivity. Retentivity is a measure of the magnetism remaining when the magnetite is removed from the magnetic field, i.e., the residual magnetism. Also, of interest is the high retentivity such that when the characters are read, the magnetites produce a signal, or signal strength of the toner composition. The magnetic signal level is of value in MICR systems, and the signal level can vary in proportion to the amount of toner deposited on the document being generated and the signal strength of the toner composition can be measured by using known devices, including the MICR-Mate 1, manufactured by Checkmate Electronics, Inc.
In forming toner compositions for use with reprographic or xerographic print devices, emulsion aggregation processes are known. For example, emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256 and 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,869,215; 5,863,698; 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488 and 5,977,210.
In addition, the following U.S. patents relate to emulsion aggregation processes for the formation of toner compositions, the disclosures of which are totally incorporated herein by reference.
U.S. Pat. No. 5,922,501 describes a process for the preparation of toner comprising blending an aqueous colorant dispersion and a latex resin emulsion, and which latex resin is generated from a dimeric acrylic acid, an oligomer acrylic acid, or mixtures thereof and a monomer; heating the resulting mixture at a temperature about equal, or below about the glass transition temperature (Tg) of the latex resin to form aggregates; heating the resulting aggregates at a temperature about equal to, or above about the Tg of the latex resin to effect coalescence and fusing of the aggregates; and optionally isolating the toner product, washing, and drying.
U.S. Pat. No. 5,945,245 describes a surfactant free process for the preparation of toner comprising heating a mixture of an emulsion latex, a colorant, and an organic complexing agent.
U.S. Pat. No. 5,482,812 describes a process for the preparation of toner compositions or toner particles comprising (i) providing an aqueous pigment dispersion comprised of a pigment, an ionic surfactant, and optionally a charge control agent; (ii) providing a wax dispersion comprised of wax, a dispersant comprised of nonionic surfactant, ionic surfactant or mixtures thereof; (iii) shearing a mixture of the wax dispersion and the pigment dispersion with a latex or emulsion blend comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and a nonionic surfactant; (iv) heating the above sheared blend below about the glass transition temperature (Tg) of the resin to form electrostatically bound toner size aggregates with a narrow particle size distribution; (v) adding additional ionic surfactant to the aggregated suspension of (iv) to ensure that no, or minimal additional particle growth of the electrostatically bound toner size aggregates occurs on further increasing the temperature to coalesce the aggregates into toner particles (vi); (vi) heating the mixture of (v) with bound aggregates above about or at the Tg of the resin; and optionally (vii) separating the toner particles from the aqueous slurry by filtration and thereafter optionally washing.
U.S. Pat. No. 5,622,806 describes a process, for example, for the preparation of toner compositions with controlled particle size comprising (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight to water, and an optional charge control agent; (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of the ionic surfactant, a nonionic surfactant, and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin, and charge control agent; and (iii) stirring.
It is a feature of the present invention to provide a magnetite containing toner for Magnetic Ink Character Recognition processes by, for example, using a specific type of magnetite to provide an acceptable readability signal by a check reader.
In another feature of the present invention, there is provided a process for the preparation of a MICR toner by an emulsion aggregation process in which the magnetite comprised of iron oxides, such as FeO and Fe2O3 pigment particles, can also function as a coagulating agent; thus the magnetite particles can exhibit negative charging characteristics in basic or high pH conditions without the need of any external coagulating agents such as anionic coagulants such as surfactants.
Another feature disclosed resides in the use of magnetite and other oxides particles, for example titanium, aluminum zirconium, which exhibit also a dual charge depending on the pH of the surrounding media, allowing the particles to be used as coagulating/flocculating agents for anionic or cationic systems. Cationic latexes with a basic pH of, for example, about 7.5 to about 10 and can readily be aggregated with a cationic wax dispersion using magnetite particles that exhibit a negative charge in basic pH conditions, thereby acting as a flocculating agent. Magnetite particles when dispersed in water in the presence of a cationic or optionally a nonionic surfactant provide a magnetite dispersion with the resulting dispersion generally neutral in pH where the pH is, for example, of about 6.5 to about 7 where the surface charge of the magnetite particle is neutral, for example about 0 to about xe2x88x922 coulombs/cm2. By introducing a basic cationic latex whose pH is about 9 to about 11 to the magnetite dispersion induces a negative charge on the magnetic particles thereby acting as a flocculating agents for the cationic species.
It is further another feature of the present invention to provide a MICR toner prepared by emulsion aggregation wherein the particle morphology can be tailored from, for example, a potato to spherical shape.
It is also a feature of the present invention to provide a MICR toner by emulsion aggregation process by the full incorporation therein of needle shape or acicular magnetite particles which are of a size diameter of about 450 nanometers to about 700 nanometers.
It is yet another feature of the present invention to provide a process that is capable of incorporating into toners needle shape or acicular magnetite which have a coercivity of about twice that of the cubic or spherical magnetite to thereby provide an adequate magnetic signal for readability by commercial check readers.
In another feature of the present invention there is provided a process for the preparation of a MICR toner by emulsion aggregation process wherein the amount of acicular magnetite loading is about 25 to about 35 weight percent of toner, and wherein the amount of spherical or cubic magnetite loadings is about 45 to about 65 weight percent to achieve a suitable MICR signal and the difference is due to size of the cubic or spherical magnetite and their magnetization power is very low. The magnetic signal is the measure of the standard calibration document as defined by the Banker""s Association Standard and Specifications for MICR Encoded Document. Generally, each country sets a minimum percent signal level, for example the minimum signal level in the USA is 50 percent of the nominal, while in Canada it is 80 percent of the nominal. To ensure latitude in the printing process, it is generally desirable to exceed the nominal specification, for example the target signal which is about 115 to about 130 percent of the nominal to minimize the document rejection rates.
Yet another feature disclosed resides in a process for preparing a magnetite dispersion comprising acicular or cubic iron oxide particles in water containing a cationic surfactant or a nonionic surfactant by ball milling, attrition, polytroning or media milling resulting in iron oxide particle stabilized by the surfactant, and wherein the dispersion is aggregated with latex particles and wax particles to obtain a MICR toner.
In another feature of the present invention there resides a process for preparing a MICR toner in which the magnetite dispersion comprising acicular iron oxide particles in water and a cationic or a nonionic surfactant in which the iron oxide particles tend to settle due to the density differences, and which particles can be redispersed by stirring, including homogenization to obtain a suitable magnetite dispersion for the preparation of MICR toners.
Aspects disclosed herein relate to a process for the preparation of a magnetic toner comprising the heating of a colorant dispersion comprised of a magnetite dispersion, and a carbon black dispersion, and thereafter mixing with a basic cationic latex emulsion and a wax dispersion; a process comprising the heating of a colorant dispersion comprised of a magnetite dispersion, and a carbon black dispersion and thereafter mixing with a latex; a toner process which comprises heating a latex emulsion with a magnetite dispersion and a carbon black dispersion wherein the heating in sequence is below the latex resin glass transition temperature and above the latex resin Tg, and wherein the magnetite is an acicular magnetite; a process comprising mixing an acicular magnetite dispersion, and a carbon black dispersion with a latex emulsion and a wax dispersion; a process for the preparation of a MICR toner wherein there are selected two dispersions of (i) a magnetite dispersion and (ii) a colorant, such as carbon black dispersion; a process comprising
(i) providing an acicular magnetite dispersion which contains water and a cationic surfactant, or a nonionic surfactant, and a carbon black dispersion of water and a cationic surfactant, or a nonionic surfactant, and wherein the pH of the dispersion is about 6.5 and wherein the latex selected is an emulsion comprised of an cationic surfactant, water and resin, and which emulsion is at a pH of about 10;
(ii) wherein the colorant dispersion is blended with the latex emulsion, and thereafter adding a wax dispersion comprised of submicron wax particles of from about 0.1 to about 0.5 micron in diameter by volume, and which wax is dispersed in a cationic surfactant;
(iii) resulting in a blend possessing a pH of about 8.5 to about 9.5 thereby inducing a negative charge on the magnetite particles to thereby initiate flocculation or aggregation of the resin latex, the colorant, and the wax;
(iv) heating the resulting mixture below about, or about equal to the glass transition temperature (Tg) of the latex resin to form toner sized aggregates;
(v) adding to the formed toner aggregates a second latex comprised of resin suspended in an aqueous phase containing a cationic surfactant and water, and stirring for a sufficient period of time to permit stabilization of the aggregate particle size;
(vi) adding to the resulting mixture an acid to thereby change the pH, which is initially from about 8.5 to about 9.5, to arrive at a pH of from about 6 to 6.8 for the resulting toner aggregate mixture;
(vii) heating the resulting aggregate suspension of (vi) above about the Tg of the latex resin of (i), while maintaining the pH at a value of about 6 to about 6.8;
(viii) retaining the mixture temperature at from about 85xc2x0 C. to about 95xc2x0 C. (degrees Centigrade) optionally for a period of about 10 to about 60 minutes, followed by a pH increase with a base to arrive at a pH of about 7 to about 8;
(ix) retaining the mixture temperature from about 85xc2x0 C. to about 95xc2x0 C. for a period of about 7 to about 14 hours to assist in permitting the fusion or coalescence of the toner aggregates and to obtain smooth particles;
(x) washing the resulting toner slurry; and
(xi) isolating the toner; a process wherein the latex resin particles are from about 0.15 to about 0.3 micron in volume average diameter; and wherein the colorant is a magnetite pigment of a size diameter of about 0.6 micron to about 0.1 micron, and the carbon black is of a size diameter of about 0.01 to about 0.2 micron in average volume diameter; the acid is selected from the group consisting of nitric, sulfuric, hydrochloric, citric and acetic acid; the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide; there is added to the formed toner aggregates a second latex comprised of submicron resin particles suspended in an aqueous phase containing a cationic surfactant, and wherein the second latex is selected in an amount of from about 10 to about 40 percent by weight of the initial latex, and forms a shell thereover on the formed aggregates, and which shell is of a thickness of, for example, about 0.2 to about 0.8 micron; wherein the added latex contains the same resin as the initial latex of (i), or wherein the added latex contains a dissimilar resin than that of the initial latex; the pH of the mixture resulting in (vi) is decreased from a pH of about 8.5 to about 9.5 to about 6 to about 6.8 with an acid, and wherein the acid functions primarily as a stabilizer for the aggregates during coalescence (vii), and no or minimal toner particle size or GSD increases result; the temperature at which toner sized aggregates are formed controls the size of the aggregates, and wherein the final toner size is from about 5 to about 15 microns in volume average diameter; the aggregation (iv) temperature is from about 45xc2x0 C. to about 60xc2x0 C., and wherein the coalescence or fusion temperature of (vii) and (viii) is from about 85xc2x0 C. to about 95xc2x0 C.; the time of coalescence or fusion is from about 12 to about 20 hours and wherein there are provided toner particles with a smooth morphology; a process for the preparation of a toner comprising (i) forming a resin latex dispersion of a resin in an aqueous cationic surfactant solution from a latex utilizing a cationic surfactant and optionally a nonionic surfactant where the latex pH is about 10 to about 11; (ii) preparing a pigment dispersion in water, and wherein the pigment is an acicular magnetite pigment dispersed in water and a cationic surfactant dispersion, and optionally a nonionic surfactant, wherein the pH of the dispersion is about 6.3 to about 7 followed by adding a cationic dispersion of a carbon black pigment; (iii) blending the resulting basic cationic resin latex dispersion of a pH of about 10 to about 11 with the pigment dispersion of (ii), followed by the addition of a cationic wax dispersion, resin/pigment/wax blend with a pH of about 9.3, thereby inducing a negative charge on the magnetite surface to initiate flocculation or aggregation of the resin, carbon black, wax particles, and magnetite particles; (iv) continuously subjecting the mixture to high shear to form a homogeneous gel of the blend; (v) heating the sheared gel at a temperature below the glass transition temperature (Tg) of the resin while continuously stirring to form aggregate particles; (vi) following a suitable period of time to permit stabilization of the aggregate particle size, adding a latex comprised of the same latex formulation as that of (i), or optionally a cationic latex comprising a different formulation than that of (i); (vii) modifying the pH of the slurry to a pH of 6 to about 6.8 to minimize any further growth of the aggregate particles of (vi); (vii) heating the aggregate particles at a temperature above the Tg of the latex resin, followed by increasing the pH of the aggregate particles to about 7 to about 8 and heating further for a period of about 7 to about 14 hours to form coalesced particles of a toner composition; and (viii) separating and drying the toner product; a toner process comprising (i) forming a basic cationic resin latex dispersion of a resin contained in an aqueous cationic surfactant solution from a latex utilizing a cationic surfactant and a nonionic surfactant, which dispersion pH is at about 10; (ii) preparing a pigment dispersion of an acicular magnetite pigment dispersed in water and a cationic dispersant, and optionally a nonionic dispersant; adding an additional cationic pigment dispersion of carbon black with a pH of about 6.5; (iii) blending about 80 to about 99 percent by weight of the total amount of the resin latex dispersion to be added in the process with the pigment dispersion mixture to which is added a cationic wax dispersion comprising wax particles suspended in water in the presence of a cationic surfactant to form a resin/magnetite/carbon black/wax blend, which blend possesses a pH of about 8.5 to about 9.5 thereby inducing a negative surface charge on the magnetite particles, which particles function as a coagulant to initiate flocculation or aggregation; (iv) continuously subjecting the mixture to high shear to induce a homogeneous gel of the blend; (v) heating the sheared gel at a temperature below the glass transition temperature (Tg) of the latex resin while continuously stirring to form toner size aggregate particles; (vi) following a period of time to permit stabilization of the aggregate particle size; (vii) adding the remaining portion of the total amount of resin latex dispersion; (vii) charging the pH of the slurry to a pH of 6.3 with an acid to stabilize the particles to growth; (viii) then heating the aggregate particles at temperatures above the Tg of the latex resin, followed by increasing the pH to about 7.5 in stages over a period of about 60 to about 90 minutes, and further heating the mixture for a period of about 7 to about 14 hours to form coalesced toner particles; and (ix) separating and drying the toner product; a process comprising mixing a colorant dispersion of acicular magnetite and a dispersion of carbon black (whose initial pH is about 6.5 wherein at the pH the magnetite particles have neutral or slightly negative surface charge), a latex emulsion with an initial pH of about 10 and a wax dispersion resulting in a blend of latex/magnetite/carbon black/wax particles with a pH of about 9.3 wherein the resulting change in the pH of the magnetite pigment dispersion induces a negative surface charge thereby functioning as a coagulant to initiate flocculation or aggregation of the, resin, carbon black and the wax particles on the surface of the magnetite particles; a process wherein the colorant dispersion is comprised of
(i) an iron oxide, water, and a cationic surfactant, or a nonionic surfactant, and a carbon black dispersion of water and a cationic surfactant, or a nonionic surfactant with a pH of about 6.5, and wherein the latex is an emulsion comprised of an anionic surfactant, water and resin with a pH of about 10;
(ii) wherein the colorant dispersion is blended with the latex emulsion, thereafter adding a wax dispersion comprised of submicron wax particles of from about 0.1 to about 0.5 micron in diameter by volume, which wax is dispersed in a cationic surfactant;
(iii) wherein the resulting blend has a pH of about 9.3 thereby inducing a negative charge on the magnetite particles to thereby initiate flocculation or aggregation of the resin latex, the colorants, and the wax when present;
(iv) heating the resulting mixture below about, or about equal to the glass transition temperature (Tg) of the latex resin to form toner sized aggregates;
(v) adding to the formed toner aggregates a second latex comprised of resin suspended in an aqueous phase containing an ionic surfactant and water, and stirring for a period of time to permit stabilization of aggregate particle size;
(vi) adding to the resulting mixture an acid to thereby change the pH which is from about 8.5 to about 9.5 to arrive at a pH of from about 6 for the resulting toner aggregate mixture;
(vii) heating the resulting aggregate suspension of (vi) above about the Tg of the latex resin of (i), while maintaining the pH at a value of about 6;
(viii) heating at about 95xc2x0 C. optionally for a period of about 10 to about 60 minutes, followed by a pH increase with a base to arrive at a pH of about 7.5;
(ix) further retaining the mixture temperature from about 85xc2x0 C. to about 95xc2x0 C. for a period of about 7 to about 14 hours to assist in permitting the fusion or coalescence of the toner aggregates to obtain smooth particles;
(x) washing the resulting toner slurry; and
(xi) isolating the toner; a process wherein the blending and aggregation are performed in the pH range of about 8 to about 9.8, and more specifically, from about 8.5 to about 9.5, while the coalescence is initially conducted in the pH range of about 6.3 to about 6.8 followed by a increase in pH to a range of about 7 to about 8 followed by further heating for a period of about 7 to about 14 hours; a process for preparing a MICR toner composition by emulsion aggregation process and which toner contains about 25 to about 35 weight percent of acicular or needle shape magnetite, and wherein there is provided smooth particles with a particle size distribution as measured on a Coulter Counter of about 1.20 to about 1.26, and wherein the toner resulting provides a MICR signal of about 1 15 to about 130 percent and a bulk remanence of about 26 emu/g wherein the remanence can be measured on a tapped powder magnetite sample in a cell of 1 centimeter by 1 centimeter by about 4 centimeters. The sample is magnetized between two magnetic pole faces with a saturating magnetic field of 2,000 Gauss, such that the induced magnetic field is perpendicular to one of the 1 by 4 centimeter faces of the cell. The sample is removed from the saturating magnetic field, and the remanence is measured perpendicular to the above 1 centimeter wide face using a Hall-Effect device or a gaussmeter, such as the F.W. Bell, Inc. Model 615 gaussmeter; a toner process wherein there is selected magnetite contained in water at, for example, a pH of about 7 to about 10 resulting in a surface charge polarity change of from about xe2x88x925 to about xe2x88x9250 coulombs/cm2, which behavior is related to the manner in which the water and the hydroxide (OHxe2x88x92) groups interact with the oxide surface; at room temperature, for example 25xc2x0 C., the magnetite surface has a point of zero charge (Pzc) corresponding to a pH of 6.5; the magnetite charge increases negatively quite strongly with increasing pH; below the Pzc, the surface charge of the magnetite increases positively with decreasing pH; at or slightly above room temperature the magnetite is negatively charged in a basic media, which negative charge causes the magnetite particles to act as a coagulating agent for the cationic latex, the cationic carbon black dispersion and the cationic wax dispersion resulting in a heterocoagulation of these components; at, for example, about 30 weight percent loading of the acicular magnetite, there is a sufficient positive charge generated to coagulate the latex, carbon black and wax; loading of less than 30 weight percent, for example 20 percent, there can be added an external coagulant, such as a metal halide, for example polyaluminum chloride, to provide narrow particle size distribution, for example 1.20 to 1.25, and wherein the point of zero charge (PZC) also moves with time, for example at 25xc2x0 C., the PZC is at a pH of 6.5, and as the temperature is increased the PZC decreases in pH where, for example, at the coalescence temperature of 93xc2x0 C. the PZC is 5.3.
The colorant dispersion is, for example, comprised of acicular magnetite particles dispersed in water, a cationic surfactant and a nonionic surfactant wherever the dispersion possesses a pH of from about 6.5 to about 6.8; the carbon black particles can be dispersed in water in the presence of a cationic or a nonionic surfactant at a pH of about 6.5 to about 6.8; the acicular magnetite is, for example, from about 20 to about 35 percent by weight of toner and in the presence of a basic cationic latex functions as a negatively charged particle thereby facilitating aggregation; and wherein the acicular magnetite amount is from about 23 to about 32 percent by weight of toner and in the presence of an acidic anionic latex acts as a positively charged particle thereby facilitating aggregation; wherein the acicular utilized exhibits a coercivity from about 250 to about 700 Oe (Osteads); wherein the acicular magnetite, which can be comprised of 21 percent FeO and 79 percent Fe2O3 is selected from the group consisting of B2510, B2540, B2550, HDM-S 7111, all available from Magnox, with a coercivity of from about 250 to about 500 Oe, whose remanent magnetization (Br) is about 23 to about 39 emu/g, whose saturation magnetization (Bm) is about 70 to about 90 emu/g; MR-BL with a coercivity of 340 Oe, a remanent magnetization (Br) of about 34 emu/g, a saturation magnetization (Bm) of about 85 emu/g, available from Titan Kogyo and Columbia Chemicals; MTA-740 with a coercivity of 370 Oe, a remanent magnetization (Br) of about 30 emu/g, a saturation magnetization (Bm) of about 83 emu/g, available from Toda Kogyo; AC 5151M with a coercivity of 270 Oe, a remanent magnetization (Br) of about 20 emu/g, a saturation magnetization (Bm) of about 79 emu/g, available from Bayer; MO08029, MO04232, MO4431 with a coercivity of from about 250 to about 400 Oe, a remanent magnetization (Br) of about 23 to about 60 emu/g, a saturation magnetization (Bm) of about 70 to about 90 emu/g, all available from Elementis, Inc.; wherein the toner exhibits a magnetic signal of from about 115 to about 150 percent of the nominal signal; a minimum fix temperature (MFT) of about 170 to about 195xc2x0 C.; a hot offset temperature (HOT) of about 210 to about 250xc2x0 C.; a process wherein the magnetite dispersion is obtained by ball milling, attrition, polytroning or media milling resulting in a stabilized magnetite or iron oxide particles in water containing an anionic surfactant; and wherein the carbon black dispersion is present in an amount of about 4 to about 8 percent by weight of toner.
Latex contains a resin or polymer selected from the group consisting of poly(styrene-alkyl acrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate), poly(styrene-alkyl acrylate-acrylic acid), poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkyl methacrylate-acrylic acid), poly(alkyl methacrylate-alkyl acrylate), poly(alkyl methacrylate-aryl acrylate), poly(aryl methacrylate-alkyl acrylate), poly(alkyl methacrylate-acrylic acid), poly(styrene-alkyl acrylate-acrylonitrile-acrylic acid), poly(styrene-1,3-diene-acrylonitrile-acrylic acid), and poly(alkyl acrylate-acrylonitrile-acrylic acid); the latex contains a resin selected from the group consisting of poly(styrene-butadiene), poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene); poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid), poly(styrene-butyl acrylate-acrylononitrile), and poly(styrene-butyl acrylate-acrylononitrile-acrylic acid); and wherein the included magnetite functions as a negatively charged coagulant.
Illustrative examples of resin particles selected for the processes illustrated herein include known polymers selected, for example, from the group consisting of poly(styrene-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methylstyrene-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methyl methacrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(ethyl methacrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(propyl methacrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(butyl methacrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methyl acrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(ethyl acrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(propyl acrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(butyl acrylate-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methylstyrene-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methyl methacrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(ethyl methacrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(propyl methacrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(butyl methacrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(methyl acrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(ethyl acrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(propyl acrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(butyl acrylate-isoprene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride); poly(styrene-propyl acrylate 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butyl acrylate 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butadiene 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butadiene-acrylonitrile 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butyl acrylate 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), poly(styrene-butyl acrylate 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride), and poly(styrene-butyl acrylate-acrylononitrile 3-metacryloxy-2-hydroxypropyltrimethyl ammonium chloride).
The resin particles selected, which generally can be in embodiments styrene acrylates, styrene butadienes, styrene methacrylates, or polyesters are present in various effective amounts, such as from about 70 weight percent to about 98 weight and, more specifically, from about 80 to about 92 percent of the toner, and which particles can be of small average particle size, such as from about 0.01 micron to about 1 micron in average volume diameter as measured by the Brookhaven nanosize particle analyzer. Other effective amounts of resin can be selected.
The resin particles selected for the process of the present invention can be prepared by, for example, emulsion polymerization techniques, including semicontinuous emulsion polymerization methods, and the monomers utilized in such processes can be selected from, for example, styrene, acrylates, methacrylates, butadiene, isoprene, and optionally acid or basic olefinic monomers such as acrylamide, methacrylamide, quaternary ammonium halide of dialkyl or trialkyl acrylamides or methacrylamide, vinylpyridine, vinylpyrrolidone, vinyl-N-methylpyridinium chloride and the like. The presence of acid or basic groups in the monomer, or polymer resin is optional, and such groups can be present in various amounts of from about 0.1 to about 10 percent by weight of the polymer resin. Chain transfer agents, such as dodecanethiol or carbon tetrabromide, can also be selected when preparing resin particles by emulsion polymerization. Other processes of obtaining resin particles of from about 0.01 micron to about 1 micron can be selected from polymer microsuspension process, such as illustrated in U.S. Pat. No. 3,674,736, the disclosure of which is totally incorporated herein by reference, polymer solution microsuspension process, such as disclosed in U.S. Pat. No. 5,290,654, the disclosure of which is totally incorporated herein by reference, mechanical grinding process, or other known processes.
Examples of cationic surfactants utilized in the colorant dispersion for the MICR toners and processes illustrated herein include, for example, dialkyl benzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride, alkyl benzyl methyl ammonium chloride, alkyl benzyl dimethyl ammonium bromide, benzalkonium chloride, cetyl pyridinium bromide, C12, C15, C17 trimethyl ammonium bromides, halide salts of quaternized polyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride, MIRAPOL(trademark) and ALKAQUAT(trademark), available from Alkaril Chemical Company, SANIZOL(trademark) (benzalkonium chloride), available from Kao Chemicals, and the like, and mixtures thereof. This surfactant is utilized in various effective amounts, such as for example, from about 0.01 to about 10 percent by weight of latex resin, and more specifically, in the range of 0.1 to about 5 percent by weight of toner.
Examples of nonionic surfactants that may be included in the resin latex dispersion include, for example, polyvinyl alcohol, polyacrylic acid, methalose, methyl cellulose, ethyl cellulose, propyl cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, dialkylphenoxypoly(ethyleneoxy) ethanol (available from Rhodia as IGEPAL CA-210(copyright), IGEPAL CA-520(copyright), IGEPAL CA-720(copyright), IGEPAL CO-890(copyright), IGEPAL CO-720(copyright), IGEPAL CO-290(copyright), IGEPAL CA-210(copyright), ANTAROX 890(copyright) and ANTAROX 897(copyright). A suitable concentration of the nonionic surfactant is, for example, from about 0.01 to about 10 percent by weight, and more specifically, from about 0.1 to about 5 percent by weight of monomers used to prepare the toner polymer resin.
Examples that are suitable for dispersing the magnetite pigment particles can be functional copolymers including, for example, methyl vinyl ether-maleic acid, methyl vinyl ether-maleic acid calcium sodium salt, hydrophobically modified polyethers, polyvinylpyrrolidone homopolymers, alkylated vinylpyrrolidone copolymers, vinyl acetate/vinylpyrrolidone copolymers, vinylpyrrolidone/styrene block, poly(methyl vinyl ether/maleic anhydride) (linear interpolymer with 1:1 molar ratio), dimethylaminoethyl methacrylate, ethylene-vinyl acetate copolymer of maleic anhydride and acrylic acid, polystyrene-maleic anhydride, styrene-acrylic ester, ethyl acrylate/methyl methacrylate, carboxylated poly-n-butyl acrylates, or ethylene vinyl alcohol, and which dispersants can in embodiments permit the magnetite to be readily dispersible into submicron particles of about 30 to about 400 nanometers in diameter in either acid or a base, and thus resulting in a magnetite that is stabilized by resin particles.
In some instances, colorants are available in the wet cake or concentrated form containing water, and can be easily dispersed utilizing a homogenizer or simply by stirring or ball milling or attrition, or media milling. In other instances, pigments are available only in a dry form, whereby dispersion in water is effected by microfluidizing using, for example, a M-110 microfluidizer or an ultimizer and passing the pigment dispersion from 1 to 10 times through the chamber, or by sonication, such as using a Branson 700 sonicator, a homogenizer, ball milling, attrition, or media milling with the addition of dispersing agents such as cationic or nonionic surfactants.
In embodiments, the multi-stage addition of latex is conducted wherein only a portion of the total amount of latex to be added into the composition is initially present. In these embodiments, a majority, for example about 60 to about 80 percent, of the latex is added at the onset while the remainder of the latex, for example about 40 to about 20 percent, (the delayed latex) is added after the formation of the resin-pigment aggregates. This delayed addition of latex can improve the formation of an outer shell of non-pigmented material around the pigmented core, thereby encapsulating the pigment in the core removed from the toner particles surface, where the presence of magnetite pigment can modify the charging behavior of the final toner particle. Homogenization is of value to ensure the formation of particles with a narrow geometric size distribution (GSD).
The toner particles may also include known charge additives in effective amounts of, for example, from 0.1 to 5 weight percent such as alkyl pyridinium halides, bisulfates, the charge control additives of U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635, the disclosures of which are totally incorporated herein by reference, and the like. Surface additives that can be added to the toner compositions after washing or drying include, for example, metal salts, metal salts of fatty acids, colloidal silicas, metal oxides, mixtures thereof and the like, which additives are usually present in an amount of from about 0.1 to about 2 weight percent, reference U.S. Pat. Nos. 3,590,000; 3,720,617; 3,655,374 and 3,983,045, the disclosures of which are totally incorporated herein by reference. Preferred additives include zinc stearate and AEROSIL R972(copyright) available from Degussa in amounts of from about 0.1 to about 2 percent which can be added during the aggregation process or blended into the formed toner product.
Developer compositions can be prepared by mixing the toners obtained with the process of the present invention with known carrier particles, including coated carriers, such as steel, ferrites, and the like, reference U.S. Pat. Nos. 4,937,166 and 4,935,326, the disclosures of which are totally incorporated herein by reference, for example from about 2 percent toner concentration to about 8 percent toner concentration.
With the process illustrated herein in embodiments, toner particles of acceptable size and narrow dispersity are obtained in a more rapid manner than disclosed in a number of prior art patents. The toner particles can possess an average volume diameter of from about 0.5 to about 30, and more specifically, from 1 to about 10 microns, and a narrow GSD characteristic of from about 1.05 to about 1.25, and more specifically, of from about 1.15 to about 1.25 as measured by a Coulter Counter. The toner product in embodiments can also possess an excellent shape factor, for example, of about 120 or less wherein the shape factor refers to the measure of toner smoothness and toner roundness, where a shape factor of 100 is considered perfectly spherical and smooth, while a shape factor of 145 is considered to be rough in surface morphology and the shape is like a potato.